Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$142.58	12.262%	$160.0632	$160.06	$160.05	$160.10
Purchase #2	$193.43	10.870%	$214.4558	$214.46	$214.45	$214.50
Purchase #3	$132.52	7.274%	$142.1595	$142.16	$142.15	$142.20
Purchase #4	$176.92	13.358%	$200.553	$200.55	$200.55	$200.60
Purchase #5	$123.52	3.185%	$127.4541	$127.45	$127.45	$127.50
Purchase #6	$208.92	9.542%	$228.8551	$228.86	$228.85	$228.90
Purchase #7	$187.45	5.686%	$198.1084	$198.11	$198.10	$198.10
7 purchase totals =	$1,165.34		$1,271.6491	$1,271.65	$1,271.60	$1,271.90